Fibronectin (hereinafter simply referred to as FN) is a glycoprotein having a molecular weight of from 430,000 to 450,000. Fibronectin is present in the cell surface, connective-tissue membranes, blood, etc. of animals.
It is known that FN has the same relative mobility as .alpha..sub.2 -globulin, an isoelectric point of 5.0, a molecular extinction coefficient A.sub.1 cm .sup.1% 280 nm of 12.9 to 13.0, S.sub.20,w of 11 to 14S, and a sugar content of 5%.
In blood coagulation, bonding between .gamma.-chains of fibrin is accelerated by transglutamination activity of blood coagulating factor XIII to form bridges of fibrin. At the same time, bridges of fibrin between .alpha.-chains are formed through FN by the catalyzing activity of the same blood coagulating factor XIII, whereby complete blood coagulation is ensured. Further, FN exhibits an activity to adhere or bind cells or sustentacular tissues among each other and is, therefore, effective to promote repairment of injuries. Other pharmacological activities of FN that have hitherto been reported include a therapeutic effect on septic shock, a therapeutic effect on infectious diseases that is attributed to heightened opsonification of phagocytes, as well as anticancer and antileukemic activity attributable to its ability to increase adhesion among cells and to necrose cancer cells. Hence, great expectations are put on FN for its clinical effects as a drug.
Moreover, in the field of ophthalmology, it has been reported in Nihon Ishikai Zasshi, Vol. 91, 560-568 (1984) that FN is effective in the therapy of various disturbances of the corneal epithelium including herpetic ulcers of the cornea.
However, FN is labile in an aqueous solution. In other words, FN in the form of an aqueous solution has low stability in terms of its biological activities and cannot be preserved as such for a long period of time. Further, when FN-containing preparations formulated into dry products are dissolved in water upon use, turbidity appears in the aqueous solution due to poor water-solubility of FN. Thus, under these circumstances, FN preparations in the form of an aqueous solution for, inter alia, eye drops having sufficient stability for clinical application have not yet been obtained.